Environmental modifications are the top tip for protecting equine respiratory safety.
by Kim F Miller
The safety of the equine respiratory system has been a hot topic amidst the terrible fires throughout the West. Horse owners in and beyond the region have had a crash course in "particulate matter," "air quality index," "inflammatory airway disease" and "equine asthma." They've learned that the impact of smoke inhalation lingers long after the fires have been contained.
One positive to emerge from the disaster is a better understanding of how the horse's respiratory system works, its vulnerabilities, how it can be protected and the subtle and not-so-subtle signs of trouble. It's important knowledge in the best of times and it's critical in the worst.
Respiratory function is greatly affected by particulate matter. Whether it's dust, fungi and bacteria found in a normal barn environment or tiny pieces of all the things -- trees, houses, cars, industrial materials -- that wildfires leave in their wake, particulate matter is a big problem.
"Particles above 5 microns in size can usually be filtered out of by natural defense mechanisms in the horse's upper airway," explains Dr. Phoebe Smith of Riviera Internal Medicine and Consulting in Santa Ynez, California.
The trachea, or windpipe, transports air from the nostrils to the lower airway passages in the horse's lungs. Built-in defenses consist of a mucus membrane and tiny, hair-like cilia that can usually trap and transport the 5-micron and over particles back out the nose or send to the esophagus to be swallowed. Such particles are about the size of a human hair. Smaller particles slip past and infiltrate the thin lining of the lung. There they irritate and inflame the surface, impeding the transfer of oxygen to the bloodstream. Along with the unusual circumstance of smoke exposure, this compromise can result from excessive quantities of large and small airborne particles that are found even in normal, seemingly healthy stables.
Fortunately, the most effective way to safeguard the respiratory system is easy: cleaning up the horse's living environment. Renowned Belgium sporthorse vet Dr. Emmanuelle Van Erck Westergren starts any case of a suspected or diagnosed respiratory issue with an assessment of the horse's habitat.
"We do measurements of dust levels and samples of contaminants," she explains of a typical barn visit for this purpose. "Some are easy to see. Have you seen someone sweep dust from the barn aisle, then stash that in the horse's stall? Or seen mold stains on barn walls or ceilings?
"A condition called Sick Building Syndrome exists in human medicine and it can apply to horses, too. They may not be coughing or having nasal discharge, but they clearly don't feel well. That can often be linked to the amount of contaminants growing inside the building.
"Horses were designed to live outside, but many horses spend 23 hours a day in the barn. Living inside, they're exposed to 50 times more inhalable irritants! Even if they live outside, if they're getting hay with contaminants, it's still a problem."
Hay and bedding are big contributors to unhealthy barn air. Because the horse's digestive physiology is best suited to a mostly forage diet, Dr. Van Erck Westergren advocates Haygain Steamed Hay. It reduces up to 99% of the dust, fungi, bacteria and other allergens found even in hay of top nutrient quality. This is a special problem because hay puts these particulates right in the horse's breathing zone.
On the stall bedding front, flooring that seals to the stall wall to prevent urine seepage and accumulation of harmful ammonia odors is ideal. ComfortStall is a top brand to feature that component and its layer of therapeutic foam reduces the need for bedding to only the amount required to absorb urine. Low-dust bedding made of cardboard (i.e. AirLite), hemp (ie. EnviroEquine), paper and other increasingly popular replacements for traditional wood shavings and straw are good options.
Found in hay, straw bedding and elsewhere in the barn, fungi is increasingly recognized as a major risk factor in respiratory health. "It can be very allergenic because it has proteins that can trigger a very strong reaction," Dr. Van Westergren explains. "It can become infectious and start to grow inside the horse's airways. That process can produce toxins and irritations to the respiratory mucosa, which can ultimately affect the throat muscles. Fungi can also trigger inflammatory responses that manifest as rhinitis and sinusitis.
"The role of fungi, aka mold, is not yet broadly recognized in the veterinary world," she continues. "When a fungal infection is suspected or diagnosed, current treatments often include corticosteroids to address inflammation. Those further depress the immune system, enhancing the opportunity for fungal infection.
"In our study of 731 horses referred for suspected respiratory issues and/or poor performance, 88% were found to have Inflammatory Airway Disease. Horses with fungal elements in their airway were 2.1 times as likely to have IAD.
"In a study we did on sport horses, we detected a link between fungi in the airways and the likelihood of Exercised Induced Pulmonary Hemorrhage: a horse is seven times more likely to bleed from the lungs, through the nose, during extreme exertion when they have fungi in the airways. In the United States, this could get a lot of attention as racetracks are in the process of phasing out Lasix, the medication that reduces EIPH."
An occasional throat-clearing cough at rest or when beginning to exercise is normal in healthy people but not in healthy horses. It's often an early sign of conditions on the mild end of the Equine Asthma Spectrum. Caught at that stage, irritation and inflammation can be undone by reducing the horse's exposure to its causes. Untreated, it can progress to more severe and potentially irreversible conditions, like Severe Equine Asthma, which can only be managed, not cured.
"Other subtle signs include nostril flair and a higher than normal respiratory rate," says Dr. Smith. "Normal is 12-24 breaths per minute, and a rate above 30 can be a symptom of trouble. Also, your horse might just seem a little off." Many veterinarians consider respiratory challenges to be the top performance limiter after soundness. This is one of many areas where knowing what's normal for your horse is essential, Dr. Smith adds.
Diagnostic tests include a rebreathing exercise in which the vet listens to lung sounds, an endoscopic exam of the airways and a bronchoalveolar lavage (lung wash) to count the number of neutrophils (inflammation indicators) that come out of the lungs.
In addition to getting oxygen into the blood stream, the lungs also function as an air filter, notes Mark Revenaugh, DVM, of Northwest Equine Performance in the Portland, Oregon, area. "If you look at an air filter in your house, you know that the more air passes through it, the dirtier it gets. The horse being a living species, however, you can't just replace the filter. It is a long process to get those particulates out of the respiratory tract."
Time and reduced exposure to inhalable particulates are nature's way of healing inflammation and the related constriction of the breathing process. It can take time to show improvement in the horse. Corticosteroids can help reduce inflammation and bronchodilators can open airways temporarily, but cleaning the horse's environment is the everyday treatment critical for ongoing healthy respiratory function.
A careful timeline for return to work is key to recovery for horses with compromised respiratory function. For the horses affected by California's recent fires, Dr. Smith prescribed between two and six weeks of rest depending on the degree and duration of their exposure to smoke. "Respiratory rest," means the horse is not breathing hard, or fast, or deeply, she clarifies. "The idea is to minimize the volume of air moving through the lungs."
As in any health concern, the horse's regular veterinarian is the first source for protecting respiratory safety, diagnosing the specific issue and recommending treatments, including how much rest before a safe return to work.
Kim F Miller is an equestrian journalist and photographer who lives in Southern California.